grab samples

C. Extraction
( I) Place I OO-ml sample in 250-ml acid-washed separatory funnel. Adjust with buffer to pH 8.0 :!::0.5
and add 2 ml of8-hydroxyquinoline solution.
(2) Extract with 3 ml MIBK, shaking thoroughly. Collect extract (top) layer in very clean glassstoppered
(or teflon) tubes for analysis.
D. Analysis
For the very low concentrations likely to be found , it will be necessary to inject MIBK-chelated metal
into the flameless attachment of the atomic absorption spectrometer. Check manufacturer's handbook for
complete details.
6.4 Cadmium (Atomic Absorption)
I. Concentrations
Average river water = « I 0 /Lg / /
Sea water = 0.0 1-0.1 I /Lg / /
The dissolved sediment as prepared in Section 6.2 is analyzed by flame atomic absorption with the
following opera ting parameters:
A. Detection Limits
Flame: 0.0 I mg/ / (solution) ( = 10 mg/ kg in sediment)
B. Working Range
Linear response of the spectrometer can be expected up to 2 mg/ / (solu tion) ( = 2 g/ kg of sediment).
C. Interferences
No serious chemical interferences.
D. Instrument Parameters
Wavelength: 228.8 nm
Fuel: air/ acetylene
Check manufacturer's handbook
Flame: oxidizing (lean, blue)
II. Solvent Extraction
This method is necessary for the low concentrations found in seawater.
A. Detection Limits
Flameless: 0.00002 mg/ / (solution)
B. Reagents
( I) Chelating reagent: ammonium pyrrolidinedithiocarbamate (APDC) or sodium diethyldithiocarbamate
(DEDC). Prepare a 5% solution with deionized-distilled water. A less concentrated solution ( 1-
2%) may be found satisfactory for many situations. Extract at least twice with methyl isobutyl ketone
(MIBK).
(2) Methyl isobutyl ketone (MIBK) (distill to purify in all glass still).
C. Extraction
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